The Lac au Sable is a body of water crossed from south to north by the Petit Saguenay River, in the unorganized territory of Mont-Élie, in the Charlevoix-Est Regional County Municipality of the administrative region Capitale-Nationale, in Quebec, Canada.

The south-eastern part of "Lac au Sable" is served by the forest road R064.

This road approaches to 0.6 km (0.37 mi) south of "Lac au Bouleau".

[2] The mouth of "Lac au Sable" is located at: From the mouth of "Lac au Sable", the current descends the Petit Saguenay River for 71.1 km (44.2 mi) north, northeast, then north to the south bank of the Saguenay River which the current then crosses on 36.6 km (22.7 mi) eastwards to Tadoussac where this last river flows into the Saint Lawrence River.

[2] The toponym "lac au Sable" was formalized on December 5, 1968, by the Commission de toponymie du Québec.